Sensitizers for photopolymerization

ABSTRACT

Aromatic-aliphatic ketones of the formulae I, II, III or IV ##STR1## wherein n is 1 or 2, Ar is an aryl radical, R 1  and R 2  are monvalent aliphatic, cycloaliphatic or araliphatic radicals, R 3  is a direct bond or a divalent organic radical, X is a hydroxyl or amino group or the monovalent etherification or silylation products thereof, and X&#39; is a divalent amino, ether or silyloxy group, Y is a direct bond or CH 2  and Z is O, S, SO 2 , CH 2  or C(CH 3 ) 2 , are suitable sensitizers for the photopolymerization of unsaturated compounds and for the photochemical crosslinking of polyolefins. Some of these compounds are novel and can be obtained by methods analogous to those for obtaining the known compounds of this type.

This application is a division of application Ser. No. 970,016, filedDec. 18, 1978.

The invention relates to the use of aromatic aliphatic ketones which aresubstituted in the α-position as sensitizers for the photopolymerisationof unsaturated compounds or for the photochemical crosslinking ofpolyolefins, as well as to the photopolymerisable and crosslinkablesystems which contain such sensitizers.

Photochemical polymerisation processes have attained substantialimportance in the art, especially in those cases where thin layers haveto be hardened in a short time, for example in the hardening of varnishcoatings or in the drying of printing inks. Compared with conventionalhardening methods, UV irradiation in the presence of photosensitizershas a number of advantages, the most important of which is the greatspeed of the photohardening. The speed is heavily dependent on thephotosensitizer employed and there has been no lack of attempts toreplace the conventional sensitizers by ever better and more effectivecompounds. Among the most effective photosensitizers are derivatives ofbenzoin, in particular the benzoin ethers described for example inGerman patent specification No. 1,694,149, derivatives ofα-hydroxymethylbenzoin described in German Offenlegungsschrift No.1,923,266, and the dialkoxyacetophenones and benzil monoketals describedfor example in German Offenlegungsschrift Nos. 2,261,383 or 2,232,365.α-Aminoacetophenones and α-diaminoacetophenones have recently have beenproposed as photosensitizers in U.S. patent specification 4,048,034 andα-hydroxy-α-alkylolacetophenones and their ethers in GermanOffenlegungsschrift No. 2,357,866. The shortcomings of these knownphotosensitizers are in some cases an insufficient storage life in thedark of the photopolymerisable systems mixed with such sensitizers. Anumber of benzoin derivatives tend to cause yellowing of the hardenedcompositions. Other sensitizers are insufficiently reactive--a featurewhich is observed in the relatively lengthy hardening times--or theirsolubility in the photopolymerisable systems is too low or they arerapidly rendered inactive by atmospheric oxygen. There is therefore aneed in the art for photosensitizers which are readily soluble in thesubstrate and, while having a good storage life in the dark, initiatethe photopolymerisation more rapidly and give a higher polymer yield perunit of time than the known photosensitizers. By using such improvedphotosensitizers it would be possible to exploit better the expensiveindustrial UV irradiation plants.

It has been found that compounds of the following formulae I, II, IIIand IV possess the required properties as photosensitizers. Inparticular, they effect a rapid photopolymerisation and do not have theshortcomings referred to or possess them to a much lesser degree thanthe known photosensitizers. Furthermore, they are suitable for thephotochemical crosslinking of polyolefins. The invention relates to theuse of the compounds of the formulae I, II, III or IV ##STR2## wherein nis 1 or 2, Ar if n is 1, represents C₆ -C₁₄ aryl which is unsubstitutedor substituted by one or more members selected from the group consistingof Cl, Br, CN, OH, C_(1-C) ₁₂ alkyl, --Oalk, --Ophenyl, --Salk, --SCH₂CH₂ OH, Sphenyl, --SO₂ alk, --SO₂ phenyl, --COOalk, --SO₂ NH₂, --SO₂NHalk, --SO₂ N(alk)₂, --NHalk, --N(alk)₂, --NHCOalk or --NHCO-phenyl, orrepresents thienyl, pyridyl, furyl, indanyl or tetrahydronaphthyl, andalk represents a lower alkyl radical of 1 to 4 carbon atoms, and if n is2, represents C₆ -C₁₂ arylene, a --phenylene-T-phenylene group or adivalent 9,10-dihydroanthracene radical, X represents one of the groups--NR⁴ R⁵, --OR⁶, --OSiR⁷ (R⁸)₂ or together with R¹ represents a--O--CH(R⁹)--, --O--CH(R⁹)--O--(CH₂)₁₋₂ -- or --O--C₁ -C₄ alkylenegroup, X' represents one of the groups --NR¹⁰ --, --N(C₆ -C₁₄ aryl)--,##STR3## --N(R¹⁰)--R¹¹ --N(R¹⁰)--, --O--, --O--R¹² --O--, --O--SiR⁷ R⁸--O--, or --O--SiR⁷ R⁸ --O--SiR⁷ R⁸ --O--, Y represents a direct bond or--CH₂ --, Z represents --O--, --S--, --SO₂ --, --CH₂ --, or --C(CH₃)₂--, T represents --O--, --S--, --SO₂ --, --CH₂ --, --CH₂ CH₂ --, --CH₂OCH₂ -- or --CH═CH--, R¹ in formula I, if n is 1 and X is --OR⁶,represents C₁ -C₈ alkyl which is unsubstituted or substituted by C₂ -C₈acyloxy, --NR⁴ R⁵, --COOalk or CN, or represents C₃ -C₅ alkenyl, C₅ -C₆cycloalkyl or C₇ -C₉ phenylalkyl, and in all other cases represents C₁-C₈ alkyl which is unsubstituted or substituted by --OH, Oalk, C₂ -C₈acyloxy, --NR⁴ R⁵, --COOalk or --CN, or is C₃ -C₄ alkenyl, C₅ -C₆cycloalkyl or C₇ C₉ phenylalkyl, R² has one of the meanings assigned toR¹ or represents a --CH₂ CH₂ R¹³ group, or together with R¹ representsC₂ -C₈ alkylene or C₃ -C₉ oxa- or azaalkylene, R³ represents a directbond, C₁ -C₆ alkylene, C₂ -C₆ oxaalkylene, C₂ -C₆ thia-, S-oxathia- orS-dioxothiaalkylene, phenylene, diphenylene or a -phenylene-T-phenylenegroup, or together with both substituents R² and both carbon atoms towhich these substituents are attached, forms a cyclopentane,cyclohexane, endomethylenecyclohexane or cyclohexane ring, R⁴ representsC₁ -C₁₂ alkyl, C₂ -C₄ alkyl substituted by --OH, Oalk or --CN orrepresents C₃ -C₅ alkenyl, cyclohexyl, C₇ -C₉ phenylalkyl, phenyl orphenyl which is substituted by Cl, alk, OH, Oalk or --COOalk, R⁵represents C₁ -C₁₂ alkyl, C₂ -C₄ alkyl which is substituted by OH, Oalkor CN or represents C₃ -C₅ alkenyl, cyclohexyl or C₇ -C₉ phenylalkyl, ortogether with R⁴ represents C₄ -C₅ alkylene which can be interrupted by--O-- or --NR¹⁴, or, in the case of compounds of the formula I, togetherwith R² represents C₁ -C₉ alkylene or phenylalkylene or C₂ -C₃ oxa- orazaalkylene, R⁶ represents hydrogen, C₁ -C₁₂ alkyl, C₁ -C₈ alkyl whichis substituted by Cl, Br, OH, Oalk, Salk, C₂ -C₈ acyloxy, --COOalk,--CONHalk, --CON(alk)₂ or CN, or represents C₃ -C₅ alkenyl, cyclohexyl,benzyl, phenyl which is unsubstituted or substituted by Cl or alk, or2-tetrahydropyranyl, R₇ and R⁸ are the same or different and representC₁ -C₄ alkyl or phenyl, R⁹ represents hydrogen, C₁ -C₈ alkyl or C₆ -C₁₄aryl, R¹⁰ represents C₁ -C₈ alkyl, cyclohexyl or benzyl, R¹¹ representsC₂ -C₈ alkylene, xylylene, phenylene or a -phenylene-T-phenylene group,R¹² represents C₂ -C₈ alkylene, C₄ -C₆ oxaalkylene or xylylene, R¹³represents --CONH₂, --CONHalk, --CON(alk)₂, --P(O)(Oalk)₂, 2-pyridyl or2-oxo-1-pyrrolidinyl, R¹⁴ represents C₁ -C₄ alkyl, --CH₂ CH₂ CN or --CH₂CH₂ COOalk, as sensitizers for the photopolymerisation of unsaturatedcompounds and for the photochemical crosslinking of polyolefins.

These compounds are accordingly aromatic-aliphatic ketones, the α-carbonatom of which is tertiary and which are substituted by a hydroxyl oramino group or the etherification or silylation products thereof. Thealiphatic residue can also be cycloaliphatic or araliphatic or linked tothe aromatic residue with ring closure, which corresponds to thebenzocyclic ketones of the formula IV.

Of the substituents listed above, R¹, R², R⁹ and R¹⁰ can be alkyl of 1to 8 carbon atoms, for example methyl, ethyl, propyl, butyl, hexyl oroctyl. R⁴, R⁵ and R⁶ as alkyl can be unbranched or branched alkyl of 1to 12 carbon atoms, for example methyl, ethyl, isopropyl, tert-butyl,isoamyl, n-hexyl, 2-ethylhexyl, n-decyl or n-dodecyl. Alk represents alower alkyl radical of 1 to 4 carbon atoms, for example methyl, ethyl,isopropyl, n-butyl or tert-butyl.

R¹, R² and R⁶ as hydroxyalkyl, alkoxyalkyl or acyloxyalkyl can be forexample hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl,2-isopropoxyethyl, 1-hydroxyisobutyl, 1-acetyloxybutyl,1-acryloyloxyhexyl, 1-hydroxyoctyl, 3-benzoyloxypropyl, methoxymethyl orisobutyloxymethyl. The acyl radical can be the radical of an aliphaticor aromatic carboxylic acid. Preferably they are 1-hydroxyalkyl radicalsand their ethers or esters. R⁴ and R⁵ as hydroxyalkyl or alkoxyalkyl canbe for example 2-hydroxyethyl, 2-butoxyethyl, 2-methoxypropyl,3-hydroxypropyl or 2-ethoxybutyl. Preferably they are 2-hydroxyalkylradicals and the ethers thereof.

R¹ and R² as alkyl which is substituted by --NR⁴ R⁵ can be for exampledibutylaminomethyl, 2-piperidinoethyl or 2-dimethylaminopropyl.

R¹, R², R⁴, R⁵ or R⁶ as CN-substituted alkyl can be for example2-cyanoethyl, 2-cyanopropyl or 4-cyanobutyl, whilst R¹, R² and R⁴ canalso be for example cyanomethyl, 2-cyanohexyl or 4-cyanooctyl. The2-cyanoethyl radical is preferred.

R¹, R² and R⁶ as alkyl substituted by --COOalk can be for example --CH₂COOC₂ H₅, --CH₂ CH₂ COOCH₃, --(CH₂)₃ --COOCH₃ or --CH₂ CH(C₂ H₅)--COOC₄H₉. R⁶ as alkyl substituted by --CONHalk or --CONH(alk)₂ can be forexample, --CH₂ CONHCH₃, --CH₂ CH₂ CON(CH₃)₂ or --CH₂ CH(CH₃)--CONHC₄ H₉.

R¹, R², R⁴, R⁵ and R⁶ as alkenyl can be for example allyl, methallyl or2-butenyl.

R¹ and R² as cycloalkyl can be cyclopentyl or cyclohexyl. R¹, R², R⁴ andR⁵ as phenylalkyl can be for example benzyl, phenylethyl ordimethylbenzyl.

Ar as aryl or substituted phenyl can be for example phenyl, naphthyl,phenanthryl, anthracyl, diphenylyl, chlorophenyl, bromophenyl,dichlorophenyl, mesityl, isopropylphenyl, phenoxyphenyl, cyanophenyl,p-nonylphenyl, hydroxyphenyl, tolyl, tert-butylphenyl, xylyl,isopropylchlorophenyl, methoxyphenyl, ethoxyphenyl, phenoxyphenyl,chlorotolyl, bromoxylyl, methylthiophenyl, phenylthiophenyl,butylsulfophenyl, phenylsulfophenyl, ethoxycarbonylphenyl,tert-butoxycarbonylphenyl, methylaminosulfophenyl,dipropylaminosulfophenyl, dimethylaminophenyl, benzoylaminophenyl oracetylaminophenyl.

R⁹ as aryl can be for example phenyl, tolyl, naphthyl, diphenylyl orphenanthryl.

R¹ and R² together can represent alkylene or oxaalkylene or azaalkylene.In this case, R¹ and R² together with the carbon atom to which they areattached form a cyclopropane, cyclobutane, cyclopentane, cyclohexane,cycloheptane, tetrahydrofurane, tetrahydropyrane, pyrrolidine orpiperidine ring.

R² and R⁵ together can represent alkylene or phenylalkylene of 1 to 9carbon atoms or oxaalkylene or azaalkylene. In this case, R² and R⁵together with the carbon atom to which R² is attached and the nitrogenatom to which R⁵ is attached form a 3- to 6-membered ring, for examplean aziridine, azetidine, pyrrolidine, imidazolidine, piperidine,piperazine or morpholine ring.

R⁴ and R⁵ together can represent alkylene of 4 to 5 carbon atoms whichcan be interrupted by --O-- or --NR¹⁴ --. In this case, R⁴ and R⁵together with the nitrogen atom to which they are attached form apyrrolidine, piperidine, morpholine, 4-alkylpiperazine,4-cyanoethylpiperazine or 4-alkoxycarbonylethylpiperazine ring.

X and R¹ together can represent a --O--CH(R⁹)--,--O--CH(R⁹)--O--(CH₂)₁₋₂ -- or --O--C₁ --C₄ alkylene group. In thiscase, R¹ and X together with the carbon atom to which they are attachedform an oxirane, oxetane, oxalane, tetrahydropyrane, 1,3-dioxolane or1,3-dioxane ring which can be substituted by alkyl or aryl.

R³ can be alkylene of 1 to 16 carbon atoms and R¹¹ and R¹² can bealkylene of 2 to 8 carbon atoms. Examples of such alkylene groups,within the stated number of carbon atoms, are: methylene, 1,2-ethylene,1,3-propylene, 1,4-butylene, 2,2-dimethyl-1,3-propylene, 1,6-hexylene,2-methyl-3-ethyl-1,4-butylene or 1,8-octylene. R³ can also beoxaalkylene, thiaalkylene and mono- or dioxothiaalkylene of 2 to 6carbon atoms, for example 2-oxa-1,3-propylene, 3-oxa-2,4-pentylene,3-oxa-2,4-pentylene, 3-oxa-1,5-pentylene, --CH₂ SCH₂ --, --CH₂ CH₂ SOCH₂CH₂ -- or --(CH₂)₃ --SO₂ --(CH₂)₃ --.

Ar can be arylene of 6 to 12 carbon atoms, for example phenylene,naphthylene or diphenylene.

If Y is a direct bond, the compounds of the formula IV constitutederivatives of indanone, cumarone or thiocumaranone. If Y is CH₂, theyare derivatives of tetralone, chromanone or thiochromanone.

A particular object of the invention is the use of compounds of theformula I or II, wherein X is a --NR⁴ R⁵ group. These compounds arearylalkyl ketones which are branched at the α-carbon atom andsubstituted by amino groups.

A further particular object of the invention is the use of compounds ofthe formula I or II, wherein X represents a --OR⁶ group. These compoundsare arylalkyl ketones which are branched in the α-position andsubstituted by hydroxyl or ether groups.

Yet a further object of the invention is the use of compounds of theformula I or II, wherein X represents a --OSiR⁷ (R⁸)₂ group. Thesecompounds are arylalkyl ketones which are branched in the α-position andsubstituted by siloxy groups. The --OSiR⁷ (R⁸)₂ group is for exampletrimethylsiloxy, dimethylphenylsiloxy, methyldiphenylsiloxy ortriphenylsiloxy.

Preferably, the invention is concerned with the use of compounds of theformulae I, II, III or IV, wherein n is 1 or 2, Ar, if n is 1,represents C₆ -C₁₄ aryl which is unsubstituted or substituted by one ormore members selected from the group consisting of Cl, Br, C₁ -C₁₂alkyl, --Oalk, --Ophenyl, --COOalk, --N(alk)₂ or --NHCOalk, orrepresents indanyl, or tetrahydronaphthyl, and alk represents a loweralkyl radical of 1 to 4 carbon atoms, and, if n is 2, represents C₆ -C₁₂arylene or a -phenylene-T-phenylene group, X represents one of thegroups --NR⁴ R⁵ or --OR⁶, X' represents one of the groups ##STR4##--N(R¹⁰)--R¹¹ --N(R¹⁰)-- or --O--R¹² --O, Y represents a direct bond or--CH₂ --, Z represents --O--, --CH₂ or --C(CH₃)₂ --, T represents --O--,--CH₂ -- or --CH₂ CH₂ --, R¹ in formula I, if n is 1 and X is --OR⁶,represents C₁ -C₈ alkyl which is unsubstituted or substituted by--COOalk or CN, or represents C₇ -C₉ phenylalkyl, and in all other casesrepresents C₁ -C₈ alkyl which is unsubstituted or substituted by --OH,Oalk, --COOalk or --CN, or is C₇ -C₉ phenylalkyl, R² has one of themeanings assigned to R¹ or is C₃ -C₄ alkenyl or a --CH₂ CH₂ R¹³ group,or together with R¹ represents C₂ -C₆ alkylene or C₃ -C₄ oxa- orazaalkylene, R³ represents a direct bond or C₁ -C₆ alkylene or togetherwith both substituents R² and both carbon atoms to which thesesubstituents are attached forms a cyclopentane or cyclohexane ring, R⁴represents C₁ -C₁₂ alkyl, C₂ -C₄ alkyl which is substituted by OH, Oalkor CN or represents C₃ -C₅ alkenyl, R⁵ represents C₁ -C₁₂ alkyl, C₂ -C₄alkyl which is substituted by OH, Oalk or CN or represents C₃ -C₅alkenyl, or together with R⁴ represents C₄ -C₅ alkylene which can beinterrupted by --O-- or --NR¹⁴, R⁶ represents hydrogen, C₁ -C₁₂ alkyl,C₁ -C₆ alkyl which is substituted by Cl, Br, OH, Oalk, --COOalk or CN,or is C₃ -C₅ alkenyl, benzyl, phenyl, or together with R² represents C₃-C₄ alkylene or --CH₂ --O--CH₂ --, R¹⁰ represents C₁ -C₈ alkyl, R¹¹represents C₂ -C₈ alkylene, R¹² represents C₂ -C₈ alkylene, C₄ -C₆oxaalkylene or xylylene, R¹³ represents --CONH₂, --CONH--alk,--CON(alk)₂, --P(O) (Oalk)₂ or 2-pyridyl, and R¹⁴ represents C₁ -C₄alkyl, --CH₂ CH₂ CN or --CH₂ CH₂ COOalk.

Among these compounds, preferred compounds are those of the formula I,especially those compounds of the formula I in which n is 1 and X is OHand R¹ and R² together represent C₂ -C₅ alkylene.

Most preferably, the invention is concerned with the use of compounds ofthe formulae I, II or III, wherein n is 1 or 2, Ar, if n is 1,represents C₆ -C₁₄ aryl which is unsubstituted or substituted byhalogen, C₁ -C₁₂ alkyl or Oalk, or represents indanyl ortetrahydronaphthyl, and alk represents a lower alkyl radical of 1 to 4carbon atoms, and, if n is 2, represents C₆ -C₁₂ arylene or a--phenylene-T-phenylene group, X represents one of the groups --NR⁴ R⁵or --OR⁶, X' represents one of the groups ##STR5## or --O--R¹² --O--, Trepresents --O--, --CH₂ -- or --CH₂ CH₂ --, R¹ represents C₁ -C₈ -alkyl,R² represents C₁ -C₈ alkyl or C₃ -C₄ alkenyl, R³ represents a directbond or C₁ -C₆ alkylene, R⁴ represents C₁ -C₁₂ alkyl, R⁵ represents C₁-C₁₂ alkyl or together with R⁴ represents C₄ -C₅ alkylene which can beinterrupted by --O-- or --NR¹⁴ --, R⁶ represents hydrogen, C₁ -C₁₂alkyl, C₁ -C₆ alkyl which is substituted by OH, Oalk, COOalk or CN, orrepresents C₃ -C₅ alkenyl, benzyl, phenyl, or together with R²represents --CH₂ --O--CH₂ --, R¹² represents C₂ -C₈ alkylene and R¹⁴represents C₁ -C₄ alkyl.

Among these compounds, those compounds of the formula I or II arepreferred in which X represents allyloxy, C₁ -C₆ hydroxyalkoxy oralkoxyalkoxy, --OCH₂ CH₂ CN, --OCH₂ CH₂ COOalk, benzyloxy or phenyloxy,or together with R² represents --O--CH₂ --O--, and also the compounds ofthe formulae I, II or III in which Ar represents p-phenoxyphenyl or atetrahydronaphthalene radical.

Examples of eligible compounds of the formula I, wherein n is 1, are:2-hydroxy-2-methyl-propiophenone, 2-hydroxy-2-ethyl-propiophenone,2-hydroxy-2-butyl-propiophenone, 2-methoxy-2-methyl-propiophenone,2-hydroxy-2-methyl-(p-chloropropiophenone),2-hydroxy-2-methyl-(3,4-dichloropropiophenone),2-hydroxy-2-methyl-(p-methoxypropiophenone),2-hydroxy-2-methyl-(2,4-dimethoxypropiophenone),2-hydroxy-2-methyl-(p-phenoxypropiophenone),2-hydroxy-2-methyl-(p-acetylaminopropiophenone),2-hydroxy-2-methyl-(p-methylpropiophenone),2-methoxy-2-methyl-(o-methylpropiophenone),2-hydroxy-2-methyl-(m-methylpropiophenone),2-hydroxy-2-methyl-(2,4-dimethylpropiophenone),2-hydroxy-2-methyl-(3,4-dimethylpropiophenone),2-hydroxy-2-methyl-(p-butylpropiophenone),2-hydroxy-2-methyl-(p-tert.-butylpropiophenone),2-hydroxy-2-methyl-(p-isopropylpropiophenone),2-hydroxy-2-methyl-(p-octylpropiophenone),2-hydroxy-2-methyl-(p-laurylpropiophenone),2-methoxy-2-methyl-(o-chloropropiophenone),2-methoxy-2-methyl-(o-methylpropiophenone),2-hydroxy-2-methyl-(p-methylthiopropiophenone),2-hydroxy-2-methyl-(p-dimethylaminopropiophenone),2-hydroxy-2-methyl-(p-carboethoxy-propiophenone),2-phenoxy-2-methylpropiophenone, 2-allyloxy-2-methyl-propiophenone,2-benzyloxy-2-methylpropiophenone,2-(2-methoxycarbonylethoxy)-2-methyl-propiophenone,2-(2-cyanoethoxy)-2-methyl-propiophenone,2-ethoxy-2-methylpropiophenone, 2-methoxyethoxy-2-methyl-propiophenone,2-hydroxymethoxy-2-methylpropiophenone,2-hydroxyethoxy-2-methylpropiophenone,2-acetoxymethoxy-2-methylpropiophenone,2-benzoyloxymethoxy-2-methylpropiophenone,2-(o-hydroxyphenoxy)-2-methylpropiophenone, 3-benzoyl-3-hydroxyheptane,2-benzoyl-2-hydroxypentane, 3-benzoyl-3-hydroxypentane,2-(2-carboethoxyphenoxy)-2-methylpropiophenone,2-methyl-2-piperidino-2-phenyl-3-hydroxypropiophenone,2-methyl-2-morpholino-3-phenyl-3-hydroxypropiophenone,2-methyl-2-dimethylamino-3-phenyl-3-hydroxy-propiophenone,α-hydroxy-α-α-bis-(cyanoethyl)-acetophenone, γ-hydroxy-γ-benzoylpimelatediethylether, 2-hydroxy-2-methyl-3-phenyl-3-dimethylaminopropiophenone,2-di-(2-hydroxyethyl)-amino-2-methyl-3-phenylpropiophenone,2-methyl-2,3-dipiperidino-3-phenylpropiophenone,2,3-bis-(dimethylamino)-3-phenylpropiophenone,2-hydroxy-2,3-dimethyl-3-phenyl-3-dimethylamino-propiophenone,2-dimethylamino-2-methylpropiophenone,2-diethylamino-2-methylpropiophenone,2-dibutylamino-2-methylpropiophenone,2-di-hydroxyethylamino-2-methylpropiophenone,2-piperidino-2-methylpropiophenone,2-(2-methylpiperidino)-2-methylpropiophenone,2-morpholino-2-methylpropiophenone, 2-piperazino-2-methylpropiophenone,2 -(4-methylpiperazino)-2-methylpropiophenone,2-(4-carboethoxyethylpiperazino)-2-methyl-propiophenone,2-pyrrolidino-2-methylpropiophenone,2-methylphenylamino-2-methylpropiophenone, 1-benzoyl-cyclohexanol,1-benzoyl-cyclopentanol,1-benzoyl-cyclopropanol-3-p-methoxybenzoyl-3-dimethylaminoheptane,6-(2-hydroxyisobutyryl)-tetraline, 5-(2-hydroxyisobutyryl)-indane,6-(2-dimethylamino-isobutyryl)-tetraline,6-(2-morpholino-isobutyryl)-tetraline,6-(2-piperidino-isobutyryl)-tetraline,6-(2-piperazino-isobutyryl)-tetraline,2-(2-methoxybenzoyl)-2-diallylaminopropane,2-(2-thenoyl)-2-piperidinopropane, 2-(2-naphthoyl)-2-acetoxybutane,2-p-phenylbenzoyl-2-di-(2-hydroxyethyl)-aminopropane,1-methyl-2-o-chlorobenzoyl-piperidin,1-benzyl-2-benzoyl-3-phenylaziridine,1-cyclohexyl-2-benzoyl-3-phenylaziridine,2-o-toluyl-2-(trimethylsiloxy)-propane,2-hydroxy-2-methyl-(p-isopropylpropiophenone),2-hydroxymethoxy-2-methyl-propiophenone,2-hydroxymethoxy-2-methyl-(2,5-dimethylpropiophenone),2-hydroxymethoxy-2-methyl-(p-isopropylpropiophenone),5-methyl-5-benzoyl-1,3-dioxolane, 2,5-dimethyl-5-benzoyl-1,3-dioxolane,2-phenyl-5-methyl-5-benzoyl-1,3-dioxolane,5-methyl-5-(p-isopropylbenzoyl)-1,3-dioxolane,2,3-epoxy-2-methyl-3-phenylpropiophenone,2-acetoxymethoxy-2-methylpropiophenone,2-benzoyloxymethoxy-2-methylpropiophenone,2-hydroxy-2-methyl-3-dimethylaminopropiophenone,2-methoxy-2-methyl-3-dimethylaminopropiophenone,2-hydroxy-2-methyl-3-morpholinopropiophenone,2-hydroxy-2-methyl-4-N,N-diethylcarbamoylbutyrophenone,2-morpholino-2-methyl-4-N,N-diethylcarbamoylbutyrophenone,2-hydroxy-2-methyl-4-(2-pyridyl)-butyrophenone,2-hydroxy-2-methyl-4-diethylphosphonobutyrophenone,2-hydroxy-2-benzylpropiophenone,2-hydroxy-2-(p-methylbenzyl)-propiophenone,2-hydroxy-2-cyclohexylpropiophenone,2-hydroxy-2-cyclopentylpropiophenone,2-(2-hydroxyethoxy)-2-methylpropiophenone,2-hydroxy-2-allylpropiophenone, 2-hydroxy-2-methyl-4-(2-oxo-1-pyrrolidinyl)-butyrophenone,2-methylthio-2-methyl-propiophenone.

Examples of compounds of the formula I, wherein n is 2, are:4,4'-bis-(α-hydroxy-isobutyryl)-diphenyl oxide,4,4'-bis-(α-hydroxy-isobutyryl)-diphenyl,4,4'-bis-(α-hydroxy-isobutyryl)-diphenylsulfide,4,4'-bis-(α-hydroxy-isobutyryl)diphenyl methane,4,4'-bis-(α-piperidino-isobutyryl)-diphenyl oxide,4,4'-bis-[α-(isopropylamino)-isobutyryl]-diphenyl,4,4'-bis-(α-benzoyloxy-isobutyryl)-diphenyl oxide,4,4'-bis-(α-hydroxy-isobutyryl)-diphenyl ethane.

Examples of compounds of the formula II are:1,4-diphenyl-2,3-dimethyl-2,3-dihydroxy-butanedione-1,4,2,4-dibenzoyl-2,4-dihydroxypentane,2,9-dibenzoyl-2,9-dimethyl-3,8-dioxadecane,2,7-dibenzoyl-2,7-dimethyl-3,6-dioxaoctane,1,6-diphenyl-2,5-dimethyl-2,5-dihydroxy-hexanedione-1,6,1,4-diphenyl-2,3-dimethyl-2,3-bis-(dimethylamino)butanedione-1,4,1,4-diphenyl-2,3-dimethyl-2,3-dipiperidylbutanedione-1,4,1,2-bis-hydroxy-1,2-bis-benzoyl-cyclohexane,1,2-bis-dimethylamino-1,2-bis-benzoyl-cyclohexane,1,2-bis-morpholino-1,2-bis-benzoyl-cyclohexane,bis-(3-hydroxy-3-benzoylbutyl)-sulfone.

Examples of compounds of the formula III are:1,4-bis-(1-benzoyl-isopropyl)-piperazine,2,7-dibenzoyl-2,7-dimethyl-3,6-dioxaoctane,2,9-dibenzoyl-2,9-dimethyl-3,8-dioxadecane,2,6-dibenzoyl-2,6-dimethyl-3,5-dioxaheptane,N,N-bis-(α-benzoyl-isopropyl)-butylamine,N,N'-dimethyl-N,N'-bis-(α-benzoyl-isopropyl)-ethylenediamine.

Examples of compounds of the formula IV are:1-oxo-2-dimethylamino-2-methyl-1,2,3,4-tetrahydronaphthalene,1-oxo-2-hydroxy-2-methyl-1,2,3,4-tetrahydronaphthalene,1-oxo-2-hydroxy-2-methylindane.

Some of the compounds of the formulae I, II, III and IV are knowncompounds, and others are novel.

Known compounds are those of the formula I, wherein n is 1, Arrepresents phenyl, phenyl which is substituted by methyl or methoxy, oris furyl, R¹ and R² are methyl or R¹ and R² together represent alkyleneand X is hydroxyl, methoxy or nitrophenoxy.

Known compounds are those of the formula I, wherein n is 1, Arrepresents phenyl, chlorophenyl or diphenylyl, R¹ and R² are methyl ormorpholinomethyl, or R¹ and R² together are alkylene and X is a --NR⁵ R⁶group, in which each of R⁵ and R⁶ is alkyl or benzyl or R⁵ and R⁶together represents alkylene or oxaalkylene.

A known compound is also a compound of the formula II, wherein Arrepresents phenyl, R¹ represents methyl, X represents hydroxy and R³ isa direct bond.

The known compounds have up to now not been proposed asphotosensitizers.

The compounds of the formulae I, II, III or IV, in so far as they arenovel, also constitute an object of the invention. Accordingly, theinvention also relates to:

(a) Compounds of the formula I, wherein n is 1, Ar represents C₁₀ C₁₄aryl, C₆ -C₁₄ aryl which is substituted by one or more members selectedfrom the group consisting of CN, OH, --Ophenyl, --Salk, --SO₂ alk, --SO₂phenyl, --COOalk, --SO₂ NH₂, --SO₂ NHalk, --SO₂ N(alk)₂, --NHalk or--NHCOalk or represents thienyl, pyridyl, indanyl or tetrahydronaphthyl,X is OH or --Oalk, and R¹ and R² are as previously defined.

(b) Compounds of the formula I, wherein n is 1, X is a --OR⁶ group andR⁶ represents C₁ -C₆ alkyl which is substituted by OH or Oalk orrepresents allyl, cyclohexyl, benzyl, phenyl which is unsubstituted orsubstituted by Cl or alk, or together with R² represents C₃ -C₄ alkyleneor --CH₂ --O--CH₂ --, and Ar, R¹ and R² are as previously defined.

(c) Compounds of the formula I, wherein n ix 1, X is --OSiR⁷ (R⁸)₂ ortogether with R¹ represents one of the groups --O--CH(R⁹)--,--O--CH(R⁹)--O--(CH₂)₁₋₂ -- or --OC₁ -C₄ alkylene, R⁷ is C₂ -C₄ alkyl orphenyl, and Ar, R¹, R² und R⁸ are as previously defined.

(d) Compounds of the formula I, wherein n is 1, Ar is phenyl,halogenphenyl or diphenylyl, X is a --NR⁴ R⁵ group, R¹ is C₂ -C₈ alkyl,C₁ -C₈ alkyl which is substituted by OH, Oalk, C₂ -C₈ acyloxy, --COOalkor CN, or is C₅ -C₆ cycloalkyl or C₇ -C₉ phenylalkyl, R² has one of themeanings assigned to R¹ or is Allyl or a --CH₂ CH₂ R¹³ group or togetherwith R¹ is C₄ --C₆ alkylene or C₃ -C₄ oxa-- or azaalkylene, and R⁴, R⁵and R¹³ are as previously defined.

(e) Compounds of the formula I, wherein n is 1, Ar is phenyl which issubstituted by CN, OH, alk, Oalk, --Ophenyl, --Salk, --SO₂ alk, --SO₂phenyl, --COOalk, --SO₂ NH₂, --SO₂ NHalk, --SO₂ N(alk)₂, NHalk,--N(alk)₂ or --NHCOalk or is naphthyl, thienyl, pyridyl, furyl, indanylor tetrahydronaphthyl, X is a --NR⁴ R⁵ group and R¹, R², R⁴ and R⁵ areas previously defined.

(f) Compounds of the formula I, wherein n is 2 and Ar, X, R¹ and R² areas previously defined.

(g) Compounds of the formula II, wherein R³ is a direct bond, X is oneof the groups --NR⁴ R⁵, --OR⁶, OSiR⁷ (R⁸)₂, R⁶ is C₁ -C₁₂ alky, C₂ -C₄alkyl which is substituted by OH or Oalk or is allyl, cyclohexyl,benzyl, phenyl which is unsubstituted or substituted by Cl or alk, andAr, R², R⁴, R⁵, R⁷ and R⁸ are as previously defined.

(h) Compounds of the formula II, wherein R³ represents C₁ -C₆ alkylene,C₂ -C₆ oxaalkylene, C₂ -C₆ thia-, S-oxothia- or S-dioxothiaalkylene,phenylene, diphenylene or a --phenylene-T-phenylene group, and Ar, R², Xand T are as previously defined.

(i) Compounds of the formula III, wherein Ar, R¹ , R² and X' are aspreviously defined.

(k) Compounds of the formula IV, wherein R¹, X, Y and Z are aspreviously defined.

These novel compounds can be prepared by methods analogous to those forobtaining the known compounds, whereby different methods are possible.

Accordingly, the compounds of the formula I can be prepared fromaromatic-aliphatic ketones by the following reaction steps: ##STR6##

As HX it is possible to use amines [C. L. Stevens, Ch. Hung Chang, J.Org. Chem. 27 (1962), 4392] or water or carboxylic acids [C. L. Stevens,E. Farkas, J. Am. Chem. Soc. 74 (1952), 618 and C. L. Stevens, S. J.Dykstra, J. Am. Chem. Soc. 75 (1953), 5976].

In many cases the direct reaction of the α-bromoketones to givecompounds of the formula I ##STR7## is also possible, for example withamines, alkali hydroxides or alkali phenoxides. Instead of brominecompounds it is also possible to use the corresponding chlorinecompounds.

The resulting hydroxyketones of the formula I (X=OH) can be etherifiedor O-silylated by the conventional methods.

Compounds of the formula III are obtained by using a difunctionalcompound of the formula H--X'--H instead of the monofunctional compoundHX in the above reactions.

The compounds of the formula II can be prepared analogously to those ofthe formula I by using diketones of the general formula ##STR8## Thecompounds of the formula IV are obtained in analogous manner startingfrom cyclic ketones of the formula ##STR9##

Compounds of the formula I, wherein R¹ is a substituted alkyl group, canbe obtained from the compounds of the formula Ar--[CO-CH(R²)-X]_(n) byreaction with aldehydes (R¹ =hydroxyalkyl) or with a vinyl compoundwhich is capable of addition, for example with acrylates oracrylonitrile. In the same way, a --CH₂ CH₂ --R¹³ group can beintroduced as R², starting from a compound Ar--[CO-CH(R¹)-X]_(n). Ifboth R¹ and R² are substituted alkyl, then both substituents can beintroduced jointly by reaction of a compound Ar--[CO-CH₂ X]_(n) with atleast 2 moles of an aldehyde or a vinyl compound. The correspondingalkoxyalkyl and acyloxyalkyl groups can be obtained from thehydroxyalkyl groups R¹ and/or R² by etherification or esterification.Compounds of the formulae II, III and IV containing substituted alkylgroups as R¹ or R² can be obtained in analogous manner.

Compounds in which X together with R¹ is a --O--CH (R⁹) group areα-oxydoketones and can be obtained by epoxidation of the correspondingα-vinyl ketones. Reaction of the oxydoketones with secondary aminesaffords compounds in which either X is OH and R¹ is an aminoalkyl group,or in which X is NR⁴ R⁵ and R¹ is a hydroxyalkyl group.

Addition of bromine to the α-vinyl ketones yields α,β-dibromoketones ofthe formula Ar--[CO-CBr(R¹)-CBralk]_(n).

Reaction of the dibromoketones with one mole of a primary amine yieldsthe corresponding α-aziridinoketones [J. Am. Chem. Soc. 65 (1943), 312],and reaction with 2 moles of a secondary amine yields compounds of theformula I, wherein X is --NR⁴ R⁵ and R² is an aminoalkyl radical [J. Am.Chem. Soc. 74 (1952), 1886].

Aminoalkyl groups R¹ and/or R² can also be introduced by the Mannichreaction, wherein ketones of the formula Ar--[CO-CHR¹ -X]_(n) orAr--[CO-CH₂ -X]_(n) are reacted with 1 or 2 moles of formaldehyde and asecondary amine.

Whereas all these methods of synthesis start from an aromatic-aliphaticketone into which a substituent X is introduced in a different manner,it is also possible in specific cases to introduce the substituent Xduring the ketone synthesis by the Friedel-Crafts reaction in accordancewith the reaction scheme: ##STR10##

This presupposes that the substituent X is not attacked uner theconditions of the Friedel-Crafts reaction. In this way it is possiblefor example by using heterocyclic carboxylic acid chlorides to preparecompounds of the formula I, in which X and R¹ together with the carbonatom to which they are attached form a heteroring.

According to the invention, the compounds of the formulae I, II, III andIV can be used as sensitizers for the photopolymerisation of unsaturatedcompounds or systems which contain such compounds.

Such compounds are for example unsaturated monomers, such as esters ofacrylic or methacrylic acid, for example methylacrylate, ethylacrylate,n- or tert-butylacrylate, isooctylacrylate or hydroxyethylacrylate,methyl or ethylmethacrylate, ethylene diacrylate, neopentyl diacrylate,trimethylolpropane trisacrylate, pentaerythritol tetraacrylate orpentaerythritol trisacrylate; acrylonitrile, methacrylonitrile,acrylamide, methacrylamide, N-substituted acrylamides andmethacrylamides; vinyl esters, such as vinyl acetate, vinyl propionate,vinyl acrylate or vinyl succinate; other vinyl compounds, such as vinylethers, styrene, alkyl styrenes, halostyrenes, divinyl benzene, vinylnaphthalene, N-vinylpyrrolidone, vinyl chloride or vinylidene chloride;allyl compounds, such as diallyl phthalate, diallyl maleate, triallylisocyanurate, triallyl phosphate or ethylene glycol diallyl ether andthe mixtures of such unsaturated monomers.

Photopolymerisable compounds are in addition unsaturated oligomers orpolymers and the mixtures thereof with unsaturated monomers. Theseinclude thermoplastic resins which contain unsaturated groups, such asfumaric acid ester groups, allyl groups or acrylate or methacrylategroups. These unsaturated groups are usually bound through functionalgroups to the main chain of these linear polymers. Mixtures of oligomerswith simply and poly-unsaturated monomers are very important. Examplesof such oligomers are unsaturated polyesters, unsaturated acrylic resinsand isocyanate or epoxide modified acrylate oligomers as well aspolyether acrylate oligomers. Examples of poly-unsaturated compounds arein particular the acrylates of diols and polyols, for examplehexamethylene diacrylate or pentaerythritol tetracrylate. Acrylates arealso preferred as simply unsaturated monomers, for example butylacrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate or2-hydroxypropyl acrylate. By choosing from the different representativesof the three components, the opportunity is afforded to vary theconsistency of the unpolymerised mixture as well as the plasticity ofthe polymerised resin.

In addition to these three-component mixtures, two-component mixturesespecially are of great importance among the polyester resins. Theseusually consist of an unsaturated polyester and a vinyl compound. Theunsaturated polyesters are oligomer esterification products of at leastone unsaturated dicarboxylic acid, for example maleic, fumaric orcitraconic acid, and usually of at least one saturated dicarboxylicacid, for example phthalic acid, succinic acid, sebacic acid orisophthalic acid, with glycols, for example ethylene glycol,propanediol-1,2, di- or triethylene glycol or tetramethylene glycol,whilst monocarboxylic acids and monoalcohols are generally also usedconcurrently for the modification. These unsaturated polyesters arenormally dissolved in a vinyl or allyl compound, styrene beingpreferably used for this purpose.

Photopolymerisable systems which are used for the different purposesusually contain, in addition to the photopolymerisable compounds and thephotosensitizer, a number of other ingredients. It is therefore oftencustomary to add heat inhibitors in order to prevent a prematurepolymerisation, especially during the preparation of the systems bymixing the components. Hydroquinone, hydroquinone derivatives,p-methoxyphenyl, β-naphthylamine or β-naphthols are used for example forthis purpose. Furthermore, small amounts of UV absorbers can be added,for example those of the benztriazole or benzophenone type.

To increase the storage life in the dark, it is possible to add coppercompounds, such as copper naphthenate, copper stearate or copperoctoate, phosphorus compounds, such as triphenylphosphine,tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzylphosphate, quaternary ammonium compounds, such as tetramethylammoniumchloride or, trimethylbenzylammonium chloride, or hydroxylaminederivatives, for example N-diethylhydroxylamine. In addition, thephotopolymerisable systems can contain chain transfer agents, forexample N-methyl-diethanolamine, triethanolamine or cyclohexene.

In order to exclude the inhibiting action of atmospheric oxygen,paraffin or similar wax-like substances are frequently added tophotohardening systems. On account of their poor solubility in thepolymer, these substances float at the beginning of the polymerisationand form a transparent surface layer which prevents the entry of air.The atmospheric oxygen can also be deactivated by introducingautoxidisable groups, for example allyl groups, into the resin to behardened.

Depending on the end-use, photopolymerisable systems also containfillers, such as silicic acid, talc or gypsum, pigments, dyes, fibres,thixotropic agents or levelling agents.

Combinations with known photosensitizers, such as benzoin ethers,dialkoxy acetophenones or benzyl ketals, can also be used. Combinationsof the photosensitizers of the invention with amines and/or aromaticketones can be used especially for the photopolymerisation of thinlayers and printing inks. Examples of amines are triethylamine,N-methyldiethanolamine, N-dimethylethanolamine orp-dimethylaminobenzoate. Examples of ketones are benzophenone,substituted benzophenone derivatives, Michler's ketone, anthraquinoneand anthraquinone derivatives, as well as thioxanthone and thederivatives thereof.

Photohardening is of great importance for printing inks, since thedrying time of the binder is a decisive factor in the production speedof printing products and should be in the order of fractions of seconds.The sensitizers of the invention are also very suitable forphotohardening systems for the manufacture of printing plates. Mixturesof soluble linear polyamides with photpolymerisable monomers, forexample acrylamides, and a photosensitizer, are usually employed forthis purpose. Films or plates prepared from these systems are exposedvia the negative (or positive) of the original and the unhardenedportions are subsequently eluted with a solvent.

A further field of use of UV hardening is metal coating, for example inthe varnish coating of metal sheeting for tubes, cans or bottle caps, aswell as the UV hardening of plastic coatings, for example of floor orwall coverings based on PVC.

Exemplary of the UV hardening of paper coatings is the colourlessvarnish coating of labels, gramophone record sleeves or book jackets.

According to the invention, the compounds of the formulae I, II, III andIV can also be used as sensitizers for the photochemical crosslinking ofpolyolefins, for example polypropylene, polybutene, polyisobutylene andalso copolymers, for example ethylene/propylene copolymers, butpreferably polyethylene of low, medium or high density.

The photosensitizers are advantageously used for the above fields of usein amounts of 0.1 to 20% by weight, preferably about 0.5 to 5% byweight, based on the photopolymerisable or crosslinkable system. Theterm "system" is to be understood as meaning the mixture of thephotopolymerisable or crosslinkable compound, the photosensitizer andthe other fillers and additives, as it is used in the respectiveapplication.

The addition of the photosensitizers to the photopolymerisable systemsis accomplished in general by simple stirring, since most of thesesystems are fluid or readily soluble. Usually the sensitizers of theinvention dissolve in the system, thereby ensuring their uniformdistribution and the transparency of the polymers.

The polymerisation is carried out by the known methods of polymerisationby irradiation with light which is rich in shortwave radiation. Suitablelight sources are for example mercury medium pressure, high pressure andlow pressure lamps, as well as superactinic fluorescent tubes, theemission peaks of which are in the range between 250 and 400 nm.

The following Examples describe the manufacture and use of compounds ofthe formula I in more detail. Parts and percentages are by weight.

Manufacture and properties of the compounds used in Examples 1 to 6

The compounds listed in Table 1 were obtained by one or more of themethods A to L.

Method A Chlorination of aromatic-aliphatic ketones

    Ar--CO-CR.sup.1 R.sup.2 H].sub.n +n Cl.sub.2 →Ar--CO-CR.sup.1 R.sup.2 Cl].sub.n +n HCl

The ketone is dissolved in an inert solvent, preferably intetrachloromethane, and the calculated amount of chlorine is introducedinto the solution at 40°-80° C. Nitrogen is then introduced to removedissolved HCl. Finally, the solvent is distilled off. Purification ofthe chloroketone is usually not necessary and the product cansubsequently be reacted by method D, F or H.

Method B Bromination of aromatic-aliphatic ketones

    Ar--CO-CR.sup.1 R.sup.2 H].sub.n +n Br.sub.2 →Ar--CO-CR.sup.1 R.sup.2 Br].sub.n +n HBr

The calculated amount of bromine is added dropwise at room temperatureto a solution of the ketone, for example in CCl₄. Working up and furtherprocessing are effected as in Method A.

Method C Chlorination with sulfuryl chloride

    Ar--CO-CR.sup.1 R.sup.2 H].sub.n +n SO.sub.2 Cl.sub.2 →Ar--CO-CR.sup.1 R.sup.2 Cl].sub.n +n SO.sub.2 +n HCl

The sulfuryl chloride is added dropwise at 40° C. to a solution of theketone in CCl₄. Working up and further processing as in Method A.

Method D Preparation of the epoxide intermediate ##STR11## Thehaloketone is dissolved in methanol and a solution of the stoichiometricamount of sodium methoxide in methanol is added dropwise at refluxtemperature. The methanol is then distilled off and the residue ispoured into ice-water and extracted with ether. The ethereal solution iswashed with water, dried over Na₂ SO₄, dried and concentrated. Theresidue is purified by recrystallisation or vacuum distillation. Theepoxide can subsequently be reacted by Method E or G. MEthod EHydrolysis of the epoxide ##STR12## The epoxide is covered with 2 to 5times its weight of water and the mixture is refluxed for 1 to 2 hourswith the addition of a catalytic amount of mineral acid. After cooling,the reaction mixture is extracted with ether. The ethereal solution iswashed with water, dried over Na₂ SO₄, and concentrated. The residue(crude hydroxyketone) is purified by distillation or crystallisation orcolumn chromatography. The properties of the pure α-hydroxyketones areindicated in Table 1. Method F α-Hydroxyketones from α-haloketones

    Ar--CO-CR.sup.1 R.sup.2 Hal].sub.n +n NaOH→Ar--CO-CR.sup.1 R.sup.2 OH].sub.n +n NaHal

The α-haloketone is refluxed in dilute or concentrated sodium hydroxidesolution (20% excess of NaOH). When the hydrolysis is complete (check bychromatography), the crude hydroxyketone is isolated and purified asdescribed in Method E. The pure hydroxyketones are listed in Table 1.

Method G α-Aminoketones from the epoxides ##STR13## The epoxide istreated with the stoichiometric amount of the amine, either without asolvent or with the addition of a small amount of toluene or xylene, andreacted for about 10 to 20 hours at 100°-200° C. When using low boilingamines, for example dimethylamine or diethylamine, the reaction iscarried out in an autoclave. The reaction mixture is diluted withbenzene and extracted with dilute hydrochloric acid. The aqueous acidsolution is made alkaline with NaOH and extracted with ether. Theethereal solution is washed with water, dried over Na₂ SO₄ andconcentrated. The crude product is purified by distillation orcrystallisation. The α-amineketones are listed in Table 1. Method Hα-Aminoketones from the α-haloketones ##STR14## The α-haloketone,undiluted or diluted with toluene, is mixed with 2 molar equivalents ofthe amine and the mixture is heated for 10 to 20 hours to 100°-200° C.When using low boiling amines, for example dimethylamine ordiethylamine, the reaction is carried out in an autoclave. Isolation andpurification are effected as in Method G. Method I Introduction of acarbalkoxyethyl group ##STR15## The ketone is dissolved in dimethylsulfoxide. To the solution are then added 1.1 molar equivalents of NaOHin the form of 4 N sodium hydroxide solution and, with cooling, 1.1molar equivalents of acrylate are added dropwise at room temperature.The reaction mixture is diluted with icewater and extracted withtoluene. The toluene solution is washed neutral with water, dried overNa₂ SO₄ and concentrated. The crude product is purified by columnchromatography or crystallisation. Method K Etherification ofhydroxyketones

    Ar--CO-CR.sup.1 R.sup.2 -OH].sub.n +n R.sup.6 Hal+n NaOH→Ar--CO-CR.sup.1 R.sup.2 -OR.sup.6 ].sub.n +n NaHal

The α-hydroxyketone is dissolved in about 4 times its weight of dimethylsulfoxide and, while cooling to 10°-20° C. and with stirring, 1 molarequivalent of the alkyl halide R⁶ Hal and 1 molar equivalent ofconcentrated sodium hydroxide solution are added dropwise simultaneouslyfrom two drip funnels. The reaction mixture is then stirred for 3 hoursat room temperature. Precipitated sodium halide is then removed byfiltration, the filtrate is washed with water, dried over Na₂ SO₄ andconcentrated. The crude product is purified by column chromatography,crystallisation or vacuum distillation. Examples of eligible halogencompounds are methyl iodide, isopropyl bromide, allyl bromide,cyclohexyl bromide, benzyl chloride or ethyl chloracetate. Instead ofusing an alkyl halide, it is also possible to use a dialkyl sulfate oralkylaryl sulfonate as etherifying reagent.

Method L Cyclisation of X and R¹ ##STR16## Paraformaldehyde is dissolvedin 20 times its weight of methanol. To the solution is then added 1molar equivalent of sodium methoxide (dissolved in a small amount ofmethanol). While cooling to 0°-5° C., a concentrated solution of theα-haloketone is added dropwise. The reaction mixture is subsequentlystirred for 1 hour at 5°-10° C. and for 1 hour at room temperature. Thereaction mixture is diluted with ether to 2 to 3 times its volume andpoured into ice-water. The aqueous mixture is extracted 3 times withether and the ethereal extracts are washed with water, dried over Na₂SO₄ and concentrated. The crude product is purified by distillation orcolumn chromatography.

                                      TABLE 1                                     __________________________________________________________________________    Com-                         Method of      Physical                          pound                                                                             Formula                  manufacture                                                                          Purification                                                                          properties (°C.)           __________________________________________________________________________         ##STR17##               B + D + G                                                                            dist.   b.p..sub.0,2 61°           2                                                                                  ##STR18##               A + D + G                                                                            cryst. (petr. ether)                                                                  b.p..sub.0,02                                                                 110- 112° m.p. 78-                                                     80° C.                     3                                                                                  ##STR19##               A + D + E or B + F                                                                   dist.   b.p. 120°                  4                                                                                  ##STR20##               B + D + E                                                                            cryst. (petr. ether)                                                                  m.p. 42-50°                5                                                                                  ##STR21##               B + D + E                                                                            chromat.                                                                              oil                               6                                                                                  ##STR22##               B + D + E                                                                            dist.   b.p.10 150°*               7                                                                                  ##STR23##               B + D + E                                                                            dist.   b.p..sub.0,1 150°*         8                                                                                  ##STR24##               B + D + E                                                                            dist.   b.p..sub.0,1 140°*         9                                                                                  ##STR25##               B + D + E                                                                            dist.   b.p..sub.0,1 130°*         10                                                                                 ##STR26##               B + D + E                                                                            dist.   b.p..sub.0.1 130°*         11                                                                                 ##STR27##               B + D + E                                                                            dist.   b.p..sub.1.0 150°*         12                                                                                 ##STR28##               B + D + E                                                                            cryst. (diethyl ether)                                                                m.p. 92-96°                13                                                                                 ##STR29##               B + D + E                                                                            dist.   b.p..sub.0.01 74°          14                                                                                 ##STR30##               C + F  chromat.                                                                              m.p. 103-105°-15                                                        C + F3dist. m.p.                                                             54-58° o.p..sub.0,1                                                    165°                       16                                                                                 ##STR32##               B + D + E                                                                            dist.   o.p..sub.0.1 150°*         17                                                                                 ##STR33##               C + D + E                                                                            dist.   o.p..sub.0.05 180°*        18                                                                                 ##STR34##               B + D + E                                                                            dist.   wax o.p..sub.0.1                                                              150°*                      19                                                                                 ##STR35##               B + D + E                                                                            dist.   b.p..sub.0.2 140°* a:                                                  β-isomer 6:1                 20                                                                                 ##STR36##               B + D + E                                                                            dist.   o.p..sub.0.1 180° *        21                                                                                 ##STR37##               B + D + E                                                                            dist.   o.p..sub.0.05 220°*                                                    wax                               22                                                                                 ##STR38##               B + F  dist.   b.p..sub.0.1 150°*         23                                                                                 ##STR39##               B + D + E                                                                            cryst. (diethyl ether)                                                                m.p. 90-91°                24                                                                                 ##STR40##               B + D + G                                                                            dist.   b.p..sub.0.1 150°*         25                                                                                 ##STR41##               B + D + G                                                                            chromat.                                                                              oil                               26                                                                                 ##STR42##               B + D + G                                                                            cryst. (ethanol)                                                                      m.p. 141-143°              27                                                                                 ##STR43##               B + D + G                                                                            dist.   b.p..sub.0.1 150°*         28                                                                                 ##STR44##               B + D + G                                                                            dist.   b.p..sub.0.1 150°*         29                                                                                 ##STR45##               B + D + G                                                                            cryst. (diisopro- pyl                                                                 m.p. 110-112°              30                                                                                 ##STR46##               C + H or A + D + G                                                                   dist.   m.p. 34°* .sub.0.05                                                    150°                       31                                                                                 ##STR47##               B + H  dist.   b.p..sub.0.1 150°*         32                                                                                 ##STR48##               B + D + G                                                                            dist.   b.p..sub.0.1 150°*         33                                                                                 ##STR49##               B + H  "       b.p..sub.0.2 180°*         34                                                                                 ##STR50##               C + H  "       b.p..sub.0.1 200°*         35                                                                                 ##STR51##               B + D + G                                                                            "       m.p. 68-71° b.p..sub.0.                                                1 210°*                    36                                                                                 ##STR52##               F      chromat.                                                                              m.p.-54°                   37                                                                                 ##STR53##               J      chromat.                                                                              oil                               38                                                                                 ##STR54##               J      chromat.                                                                              oil                               39                                                                                 ##STR55##               K      chromat.                                                                              oil                               40                                                                                 ##STR56##               K      chromat.                                                                              oil                               41                                                                                 ##STR57##               B + D + G      m.p. 38-41°                42                                                                                 ##STR58##               C + L  dist.   b.p..sub.24                       __________________________________________________________________________                                                130°                        *temperature of the air bath in bulb tube destillation.                  

EXAMPLE 1

A resin mixture consisting of 80 parts of Plex 6616 (acrylate resin,available from Rohm, Darmstadt), 20 parts oftrimethylolpropane-trisacrylate and 2 parts of photosensitizer isapplied with a film drawing device to glass plates in a thickness of40μ. These films are exposed to air for about 20 seconds and thenirradiated with a mercury medium pressure lamp (Hanovia device, Model45080). In the course of the irradiation, the samples are passedunderneath the lamp on a conveyer belt at a speed such that theeffective exposure time is 0.16 second per run.

Table 2 indicates the number of runs (R) which were necessary in orderto obtain non-tacky films. In addition, the hardness of the film wasdetermined with a pendulum device by the method of Konig. The finalcolumn indicates the storage stability of the resin-photosensitizermixture in the dark at 60° C.

                  TABLE 2                                                         ______________________________________                                                                             Stor-                                                                         age                                                        Pendulum hardness accord-                                                                        stabil-                                                    ing to Konig after ity                                      Photosensitizer                                                                          Runs   number of runs (R) in days                                  ______________________________________                                        1          4      78(4R)   94(6R) 98(8R) >30                                  2          4      101(4R)  114(4R)                                                                              116(8R)                                                                              >30                                  3          4      116(4R)  119(8R)                                                                              131(8R)                                                                              >30                                  12         3      95(3R)   101(4R)                                                                              103(5R)                                     24         3      73(5R)                                                      26         3      95(3R)   102(4R)                                                                              107(5R)                                                                              >30                                  37         4      47(3R)   72(4R) 88(5R) >30                                  α-hydroxypro-                                                                      3      68(3R)   75(4R) 87(5R) 1                                    piophenone                                                                    (comparison)                                                                  α-methylbenzoin                                                                    5      49(3R)   69(4R) 91(5R)                                      (comparison)                                                                  benzoin-tert-                                                                            5      93(5R)   106(7R)                                                                              113(9R)                                                                              <30                                  butylether                                                                    (comparison)                                                                  2-phenyl-di-                                                                             6      112(6R)  121(8R)                                                                              130(10R)                                                                             >30                                  methoxyaceto-                                                                 phenone                                                                       (comparison)                                                                  p-methyl-α,α-di-                                                             8      92(8R)   100(10R)                                                                             109(12R)                                                                             <5                                   morpholinoace-                                                                tophenone                                                                     (comparison)                                                                  α,α-dimorpholino-                                                            17     84(17R)  98(19R)       <1                                   acetophenone                                                                  (comparison)                                                                  ______________________________________                                    

EXAMPLE 2

Resin mixtures consisting of 60 parts of Uvimer DV-530 (urethaneacrylate, available from Polychrome), 37 parts of hexanedioldiacrylateand 3 parts of photosensitizer were applied in a film thickness of 30 μmto glass plates and irradiated as described in Example 1. The followingresults were obtained.

                  TABLE 3                                                         ______________________________________                                                  No. of runs    Pendulum hardness                                              necessary until wipe-                                                                        according to Konig as                                Photosensitizer                                                                         proof          a function of R                                      ______________________________________                                        1         3              129(3R)                                                                       157(7R)                                              2         3              144(3R)                                                                       163(7R)                                              diethoxyaceto-                                                                          10              156(10R)                                            phenone                                                                       (comparison)                                                                  benzion tert-                                                                           12              136(12R)                                            butyl ether                                                                   (comparison)                                                                  2-phenyldi-                                                                             8              155(8R)                                              methoxyaceto-                                                                 phenone                                                                       (comparison)                                                                  ______________________________________                                    

EXAMPLE 3

2% of photosensitizer was dissolved in an unsaturated polyester resin(Crystic PKE 306, available from Maeder, Killwangen, Switzerland). Theseresin mixtures were applied in a film thickness of 60 μm to glassplates. The films were irradiated as described in Example 1. The numberof runs through the exposure device until the films were wipe-proof aswell as the pendulum hardness as a function of R are reported in Table4.

                  TABLE 4                                                         ______________________________________                                                No. of runs  Pendulum hardness                                        Photo-  necessary until                                                                            according to Konig as                                    sensitizer                                                                            wipeproof    a function of R                                          ______________________________________                                        1       13           21(13R)  34(15R)                                                                              62(17R)                                  2        8           20(8R)   31(10R)                                                                              89(12R)                                  3       10           28(10R)  71(12R)                                                                              109(12R)                                 ______________________________________                                    

EXAMPLE 4

A resin mixture consisting of 90 parts of Laromer LR 8496 (acrylateresin available from BASF, West Germany), 10 parts of hexanedioldiacrylate, 0.5 part of Byk 300 (levelling assistant available fromByK-Mallinckrodt, West Germany) and 3 parts of photosensitizer forhardening in the air or 0.5 part of photosensitizer for hardening undernitrogen, is applied electromotively to cardboard boxes with a 15μhelix. After brief exposure to air, hardening is effected with a UVdevice (model PPG-QC-processer) with a UV lamp of 80 watts/cm. Themaximum transportation speed at which non-tacky films were obtained inair or under nitrogen is reported in Table 5 in m/min.

                  TABLE 5                                                         ______________________________________                                                       Transportation speed (m/min)                                   Photosensitizer air        nitrogen                                           ______________________________________                                        3               20         100                                                5               20         100                                                7               30         100                                                8               30         100                                                9               5          80                                                 10              5          80                                                 12              3.3        80                                                 13              20         120                                                29              10         90                                                 30              20         90                                                 ______________________________________                                    

EXAMPLE 5

A resin mixture consisting of 70 parts of Ebercyl 593 (polyesteracrylate available from UCB, Belgium), 30 parts of trimethylolpropanetrisacrylate, 0.5 part of ByK 300 (levelling assistant available fromByK-Mallinckrodt, West Germany) and 3 parts of photosensitizer, isapplied to glass plates in a layer of 30-40μ,. After brief exposure toair, hardening is effected with a UV laboratory device (modelPPG/QC-processer) with a UV lamp of 80 watts/cm. After the UV hardening,the plates are stored for 1/2 hour under normal climatic conditions andthen the hardness of the layers is determined using the pendulum deviceof Konig. The hardness values as a function of the transportation speedunder the lamp are reported in Table 6.

                  TABLE 6                                                         ______________________________________                                                      Pendulum hardness in sec.                                       Photosensitizer                                                                              10 m/min.   25 m/min.                                          ______________________________________                                         3             154         146                                                13             156         147                                                14             138         137                                                15             150         132                                                16             161         152                                                17             160         144                                                21             155         143                                                22             151         127                                                27             162         154                                                30             129          98                                                32             146         129                                                35             134         108                                                38             139         116                                                39             162         149                                                40             153         131                                                41             164         152                                                ______________________________________                                    

What is claimed is:
 1. A compound of the formula ##STR59## where Ar is4-halophenyl,X represents --OR⁶, R¹ represents alkyl of 1 to 8 carbonatoms, R² represents alkyl of 1 to 8 carbon atoms or R¹ and R² togetherrepresent alkylene of 4 to 6 carbon atoms, and R⁶ represents hydrogen oralkyl of 1 to 12 carbon atoms.
 2. A compound according to claim 1, saidcompound being 2-hydroxy-2-methyl-(p-chloropropionphenone).